I did some research awhile back on the different types of spark plugs. From what I gathered was that between the three types (standard, platinum and iridium) the standard type had the better conductor at the tip, causing a better spark thereby burning fuel more efficiently. It's downside was longevity. You will have to change the plugs much more frequently. Platinum has a much longer life than standard plugs but the material used in the tip is an alloy (combined metals) with a much greater resistance value. In other words, less spark at the tip. Iridium plugs are a different alloy with lower resistance than platinum plugs (hence greater spark) but not as low as a standard plug. Iridium plugs are said to have the same life span as platinum plugs. (2 to 3 times the life of standard plugs) From what I've read the average person is not going to notice any appreciable difference in performance in any of the different types.
On the other hand... I've not found a whole lot of reviews on the new Pulstar plugs we see advertised on the forum. They look promising but are very expensive.